Hiram s



1 UNITED STATES PATENT OFFICE.-

HIRAM S. MAXIM, OF BROOKLYN, ASSIGNOR TO THE CNITED STATES ELECTRICLIGHTING COMPANY, OF NEW YORK, N. Y.

PROCESS OF MANUFACTURING CARBON CONDUCTORS.

SPECIFICATION forming part of Letters Patent No. 247,085, datedSeptember 13, 1881. v

Application filed May 12, 1881.

To all whom it may concern Be it known that I, HIRAM S. MAXIM, ofBrooklyn, in the county of Kings and State of New York, have inventedcertain new and useful Improvements in the Process of ManufacturingCarbon Conductors for Incandescent Lamps, of which the following is aspecification.

In the usual method of manufacturing incandescent lamps the conductorsare formed from blanks cut out from sheets of paper, wood, or equivalentmaterial, which are carbonized at a high temperature in a closed mufiie.The resulting carbons, while possessing in otherrespects many of thosequalities which render them especially adapted for incandescentlighting, vary considerably in resistance, so that when included in anelectric circuit they emit widely-varying intensities of light. To bringthem all to the same resistance a current of electricity is caused topass through them while surrounded by an attenuated atmosphere ofhydrocarbon or other vapor, thus producing a deposit of carbon on theheated portions of the strips, which is kept up until the resistance ofeach individual strip is brought to a predetermined standard.

It is very necessary that all parts of the carbon conductors should betreated alike, so as to be as nearly homogeneous as possible; but withall the previously-adopted methods of manufacture this prerequisite isonly partially attained, for the reason that the enlarged or widenedends retained by the clamps in the carbon-depositing receiver are notheated as much as the slender portion of the conductor, besides beingnearly, if not quite, covered by the clamps. The narrow portion alone,then, of the strip receives the deposit of carbon, while the ends areleft in their original condition. Now, it is very essential that theenlargements at the ends should be of considerable length, in order thatthe retaining-clamps may be protected from heat, and it'is equallyessential that these ends should be of the same quality of carbon as theremainder of the strip. To produce a carbon in which these conditionsare fulfilled is, then, the object of my present invention, whichconsists of the following steps, performed in the order indicated.

(N0 model.)

I first cut out from sheets of wood, paper, or other proper fibrousmaterial, straight, narrow strips, which are packed in amuffleandcarbonized in the same mannerin which the blanks are commonly treated.After being thoroughly charred the strips are placed in a closedreceiver from whence the air has been exhausted and an attenuatedatmosphere of hydrocarbon or similar vapor substituted, and an electriccurrent passed through them sufficient to heat them to a bright red. Inthis condition they are allowed to remain until, by the deposition ofthe surrounding particles of carbon, their resistance, as indicated by agalvanometer, is reduced to a predetermined standard. From the stripsthus prepared the conductors are cut in a variety of ways-as, forinstance, one or more of the sheets may be confined between gage-platesand the projecting portions of the carbon cut or filed away. This may bedone without injury to the strips,'from the peculiar nature of thecarbon, which is hard and tough when prepared by the above-describedprocess. It is evident that in' this way a conductor is obtained inwhich all portions have been subjected to the same treatment and possessthe same relative resistance, resilience, and tenacity. The broadenedends may be cut as long as is necessary to protect the clamps from heat,so that copper and other metals than platinum may be used for thesupporting wires of the carbons.

If the character of the lamp for which the conductors are designed besuch as to make a loop or arch shaped carbon desirable, they may be bentto this form after being prepared by the process described, and thengiven a permancnt set by passing a strong current through them whilebent.

In a previous application I have described a method of producing thecarbon conductors of incandescent lamps, in which the said conductorswere out from sheets of carbonized wood or paper and then treated in theusual manner bya current of electricity passed through them whilesurrounded by an attenuated atmosphere of hydrocarbon vapor. Thismethod, however, differs essentially from the present, and I lay noclaim to it in this application.

IOC

Having thus described my invention, what 1 claim as new, and desire tosecure by Letters Patent, is

The process of manufacturing carbon con- 5 ductors for incandescentlamps by first carbonizing thin sheets or strips of fibrous material,then heating the same in a carbonaceous gas or vapor until theirelectrical resistance is reduced to a predetermined standard, and,

lastly, cutting or otherwise forming from the 10 said sheets theconductors of the desired shape, substantially as and for the purposeset forth. In testimony whereof I have hereunto set my hand this 10thday of May, 1881.

HIRAM S. MAXIM. Witnesses:

W. M. ALLAIRE, PARKER W. PAGE.

